1. Field of the Invention
The present invention relates to a method utilized in a wireless communication system and communication device thereof, and more particularly, to a method of improving semi-persistent scheduling resources reconfiguration and communication device thereof.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs). The radio protocol stacks of E-UTRAN is given including a radio resource control layer (RRC), a packet data convergence protocol layer (PDCP), a radio link control layer (RLC), a medium access control layer (MAC), and a physical layer (PHY).
In order to utilize shared channel (SCH) resources efficiently, a semi-persistent scheduling (SPS) function is introduced in the LTE system and is used in MAC, for serving upper layer applications which generate semi-static size data periodically, e.g. VoIP services. SPS resources are semi-static resources including physical resource block (PRB), modulation and coding scheme (MCS), and periodicity. Periodicity is configured by RRC, and a valid set of PRBs and MCSs is configured by RRC and selected by a physical downlink control channel (PDCCH) signaling sent from the E-UTRAN. According to current 3GPP specification, there is only an SPS pattern, i.e. periodicity, for frequency division duplex (FDD), and may exist multiple SPS patterns for time division duplex (TDD) so that SPS resources can be reconfigured to add one more SPS pattern.
An RRC connection reconfiguration procedure is used to modify an RRC connection, e.g. to establish/modify/release radio bearers, to perform handover, or to setup/modify/release measurements. When the UE receives an RRC connection reconfiguration message including an information element (IE) “mobilityControlInformation”, which includes parameters relevant to network controlled mobility, the UE performs an RRC connection reconfiguration procedure as a handover procedure. In the handover procedure, the UE deactivates any SPS resource if there is any SPS resource active and performs a radio resource configuration procedure in which SPS resources reconfiguration is performed when the RRC connection reconfiguration message includes an IE “radioResourceConfiguration”. Therefore, the UE can apply new SPS resources configuration after switching to a target cell. SPS resources reconfiguration intends that SPS cell radio network temporary identifier (SPS C-RNTI) which is the UE specific identity assigned by RRC for activation/modification of SPS resources is changed, periodicity is changed, an SPS pattern is added or removed for TDD, or a valid set of PRBs and MCSs is changed.
In addition, SPS resources may need to be reconfigured due to which a new service is activated or a service is released in the condition except the handover procedure. For example, when a VoIP service is initiated, SPS resources are usually configured for most common VoIP packet size, and when a streaming service is activated during the VoIP service, SPS resources have to be reconfigured with a large transport block size, i.e. PRBs or MCS, or a small SPS periodicity, to serve both the VoIP service and the streaming service simultaneously. The E-UTRAN can activate or modify SPS resources by sending a PDCCH signaling including SPS C-RNTI. However, SPS resources reconfiguration is not clearly specified in the RRC connection reconfiguration procedure which does not include the IE “mobilityControlInformation”, such that SPS resources reconfiguration is exactly performed only in the handover procedure.
Note that, for the LTE system, there is a timing issue that activation time of SPS resources is not included in any RRC message, and thus the UE does not know when to switch to new SPS resources. When the UE reconfigures SPS resources in the condition except the handover procedure, the UE may continue using prior SPS resources that are already released to receive transport blocks until receiving the PDCCH signaling, which causes the received transport blocks to be unsuccessfully decoded.